Transmission control



H. BROCK ETAL Original Filed June 27, 1950 '7' Sheets-Sheet l 1HLBROCK J. RS TEVENSON INVENTOR.

Aime/525m Jan. 26, 1954 H. L. BROCK ETAL TRANSMISSION CONTROL 7 Sheets-Sheet 2 Original Filed June 27, 1950 HLQBROCK J.R$TEVEN5DN INV TOR.

ATTORNEYS Jan. 26, 19 54 BRQCK ETAL 2,667,082

TRANSMISSION CONTROL Original Filed June 27, 1950 '7 Sheets-Shed 3 A H L. BROCK J. R. SJ'EVENSON IN V EN TOR.

. AT7URNEV$ Jan. 26, 1954 H. L. BROCK ET AL TRANSMISSION CONTROL Sheets-Sheet 5 Original Filed June 27, 1950 HLB/QOC/f J RSTEVENSON 4 INVE TOR. Ea

AFTOIQ/VEVS 1954 H. L.BROCK ETAL 2,667,082

TRANSMISSION CONTROL Original Filed June 27, 1950 7 Sheets-Sheet 6 Er; E E117- HLSBROCK K J. RSTEl ENSUN ATTORNEYS 26, 5 H. L. BROCK ETAL 2,667,082

TRANSMISSION CONTROL Original Filed June v27, 1950 7 Sheets-Sheet 7 SECOND V V i a m9 I 1E7, m /52 1 I a /e/ high 7 H2 EF fiyA- 'I/ a I56 Low RANGE HIGH RANGE LOW RANGE HIGH RA NGE NEUTRAL L W RANGE RE VERSE LOW RANGE V FOURTH ATTORNEYS Patented Jan. 26, 1954 TRANSMISSION CONTROL Harold L. Brook, Detroit, and James R. Stevenson,

Ann Arbor, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Original application June 27, 1950,- Serial No'.

170,658. Divided and this application November 29, 1951, Serial No. 259,744

7 Claims.

This invention relates generally to variable speed transmissions for motor vehicles.

The transmission of the present invention is particularly adapted for use in agricultural tractors, and an object of the invention is therefore to provide a transmission having a relatively large number of forward and reverse gear ratios in order that a suitable ratio will be available for each type of tractor operation. It is a further object of the invention to provide a transmission obtaining the necessary speed ratios with a minimum number of gears and with a compact arrangement. In the present construction six forward and two reverse ratios are obtained with a transmission having only eleven gears compactly arranged upon four shafts so that the distances between the bearings for each shaft can be held to a minimum.

Another object of the invention is to provide a transmission in which gear ratios can be obtained for various operational requirements, with the proper steps being provided from a very low or creeping speed to a relatively high road or transport speed. In the present construction the speed ratios are not obtained in the usual manner of a step transmission in wh ch, for example, a

'three speed transmission is provided With a reduction gear which can be inserted in the gear train to give a fixed reduction for each of the three regular speed ratios and thus provide a siX speed transmission. While a transmission of this type is easily designed and manufactured, the speed ratios thus obtained are necessarily in mathematical progression and are not the proper ratios for the rsost efficient overall operati n. W lie the present transmission provides two ranges in the shifting pattern, namely a low range and a high range, the ratios in the two ranges are not comparable to those of the usual step transmission, but are designed to provide the proper gear ratios for the various tractor operations. The particular design and arrangement of the gearing makes this possible.

Still another object of the invention is to provide simplified shifting mechanism enabling the to be shifted between the various speed ratios easily and positively with a single gearshift lever.

Another object is to provide a shift pattern of a type generally familiar to the average individual and provided with visual indicating means enabling the tractor driver to tell at a glance the gear ratio the tractor is operating in at the moment and also the shift pattern to follow to reach any other desired speed range,

SEX

Yet another object of the invention is to provide a transmission of the type mentioned in which positive interlocking means are provided to automatically hold inoperative the shift mechanism for all ratios other than that selected, and also to provideaninterlockingarrangement preventing the engine starter from being applied except when the transmission is in neutral.

The foregoing and other objects of this invention will be made more apparent as this description proceeds, particularly when considered in connection with the accompanying drawings, wherein:

Figure 1 is a side elevational View of the rearward portion of a tractor incorporating'the transmission of the present invention, with parts broken away and in section.

Figure 2 is a transverse cross sectional View taken on the line 22 of Figure 1.

Figure 3 is an expanded cross sectional view of the transmission gearing, and comprises a section taken on the line 3'--'3 of Figure 2.

Figure 4 is an enlarged vertical cross sectional view of the transmission taken longitudinally through the transmission housing just inside the left hand side of the latter.

Figure 4A is a fragmentary cross sectional view through the rearward end of shift rail 21.

Figure 5 is a transverse vertical cross sectional view taken on the line 5-5 of Figure iand showing the shifter shaft in its uppermost position.

Figure 6 is a cross sectional View similar to a portion of Figure 5 but showing the shifter shaft in its intermediate or central position.

Figure 7 is a cross sectional View similar to Figures 5 and shut showing the shifter shaft in its lowermost position.

Figure 8 is a horizontal cross sectional view taken on the line 8-8 of Figure 5 showing the upper shift arm in position to shift the transmission between first and second speeds in low range.

Figure 8A is a view similar to Figure 8 but showing the upper shift arm in position to shift the transmission between third and fifth speeds in high range.

Figure 9 is a horizontal cross sectional view taken on the line 99 of Figure 6, showing the upper shift arm in position to shift the transmission into low range neutral.

Figure 9A is a view similar to Figure 9 but showing the upper shift arm in position to shift the transmission into high range neutral.

Figure 10 is a horizontal cross sectional view taken on the line til -I ii of Figure 7, showing the 3 lower shift arm in position to shift the transmission between reverse and fourth speed in low range.

Figure 10A is a view similar to Figure 10 but showing the lower shift arm in position to shift the transmission between reverse and sixth speed in high range.

Figure 11 is a vertical cross sectional view taken on the line of Figure 6 showing the upper interlock.

Figure 12 is a horizontal cross sectional view taken on the line |2--|2 of Figure 6, showing the lower interlock.

Figure 13 is a horizontal cross sectional view taken on the line |3-|3 of Figure 6, showing the starter interlock.

Figure 14 is a transverse cross sectional view thro gh the transmission taken on the line 4--|4 of Figure 4.

Figure 15 is a front elevational view of the shift pattern plate.

The following description will deal first with the transmission gearing and next with the gearshifting and interlocking mechanism.

Transmission gearing Referring particularly to Figures 1, 2 and 3 of the drawing, the rearward portion of the tractor chassis comprises the clutch housing H and a transmission and rear axle housing l2 suitably bolted together. The housing |2 supports a rear axle l3 carrying road. wheels l4 at opposite sides of the tractor. A spring supported seat i is mounted upon housing I2 rearwardly of the dash i! and steering wheel l8.

The transmission of the tractor is mounted in the forward portion of the housing 2, and conventional rear axle and differential mechanism, including a ring gear IQ of the hypoid type, are mounted in the rearward portion of the ho sin As best seen in Figures 2 and 3, the transmission includes four longitudinally extendin shafts, namely a driveshaft 2|, 2. countershaft 22, a driven shaft 23. and an idler shaft 24. In the present construction the driveshaft 2| is in the l ke. For the purposes of this description the sleeve 2| will be termed a driveshaft.

The driveshaft 2! is journaled at its forward end in a bearing 2'! supported in the front wall 28 of the housing I2 and the rearward end of the shaft is ,iournaled in a bearing 29 supported in an intermediate wall 3| extending transversely of the housing l2 and integrally formed therewith. The driveshaft 2| has a gear 32 formed inte rally thereon near its forward end. Rearwardly of the gear 32 the driveshaft is formed with clutch teeth 33, and rearwardly of the clutch teeth 33 the driveshaft 2| is reduced in diameter and rotatably supports a cluster gear 34 freely rotatable upon the driveshaft by means of bushings The cluster gear 34 has narrow clutch teeth 3'! formed at its forward end and is also integrally formed with axially spaced gears 38 and 39.

The countershaft 22 is likewise journaled in bearings 4| and 42 supported in the transverse walls 28 and 3| of the transmission housing. At the forward end of the countershaft 22 a gear 43 is rotatably mounted and has integrally formed therewith narrow clutch teeth 44. Also freely rotatably mounted upon the countershaft 22 is a gear 46. Clutch teeth 4! and 48 are formed tritegrally with the gear 46 on opposite sides thereof. Rearwardly of the gear 46, a clutch member 49 having gear teeth formed on its periphery is splined to the countershaft 22. A gear 53 having clutch teeth 5| is freely rotatable upon the countershaft 22 rearwardly of the clutch member 49, and adjacent thereto is a gear 52, the latter, however, being splined to the countershaft 22.

The driven shaft 23 is positioned directly beneath the driveshaft 2| but is considerably shorter in length since it supports only two gears and a single clutch member. The driven shaft 23 is journaled at its forward end in a bearing 53 supported in an intermediate transverse wall 54. The wall 54 is integrally formed with the housing l2 and extends transversely across the lower portion of the latter. The rearward portion of the driven shaft 23 extends through and is journaled in bearings 56 supported in an offset portion of the transverse wall 3| of the housing. Rearwardly of the housing wall 3| the driven shaft carries a drive pinion 51 of the hypoid type which meshes with the hypoid gear I 9 of the rear axle mechanism. Adjacent the forward end of the driven shaft 23 the shaft rotatably supports a gear 58 having formed integrally therewith narrow clutch teeth 59. A clutch member 6| is splined to the driven shaft 23 adjacent the gear 58, and rearwardly thereof a gear 62 is fixedly splined to the driven shaft.

The lowermost shaft in the transmission housing is the idler shaft 24. This shaft is fixedly mounted in the transmission housing, its for ward end being supported in the intermediate wall 54 of the housing and its rearward extremity being supported in and pinned to the wall 3| of the housing. The shaft is thus held against rotation. Rotatably mounted upon the idler shaft 24 by means of bushings 63 is the hub 64 of a gear 65. A second gear 61 is rotatably mounted upon the hub 64 of the gear 63 and is integrally formed with narrow clutch teeth 58. Forwardly of the gear 61 a clutch member 69 is splined to the hub 64 of the gear 63.

Although Figure 3 is an expanded cross sectional view of the transmission gearing, all of the gears are shown in their proper meshing engagement with the exception of gear 50 on countershaft 22 and ear 61 on idler shaft 24. In Figure 3 these two gears are shown spaced from each other, but it will be noted from the transverse cross sectional view of Figure 2 that gears 50 and 61 are actually in constant mesh with each other. Bearing this in mind, Figure 3 can be used to trace the power flow through the transmission gears in the various speed ratios. Before tracing the power flow. however, the function of the various clutches will be briefly described.

Referring first to the clutch on the driveshaft 2|, a peripherally grooved clutch ring 1| is provided with internal teeth and. is adapted to slide axially on clutch teeth 33 formed on an enlarged portion of the shaft. It will be seen that when clutch ring H is shifted rearwardly (to the right in Figure 3) from the position shown in this figure, the clutch ring engages clutch teeth 37 carried by the cluster gear 34 and. is effective to lock the cluster gear to the driveshaft 2|. With the clutch ring if in the position shown in Figure 3, however, the cluster gear is not coupled to the driveshaft.

Referring now to the countershaft 22, a clutch ring 12, when shifted to the left from the posi- F PF 512935 1 in Figure 3, engages the clutch teeth 41 on the gear 43 and the clutch teeth 44 on the gear 43. In this position the gears 43 and 46 are coupled together and rotate as a unit. With the clutch ring E2 in the position shown in Figure 3 the gears #33 and i5 rotate independently of each other and are not coupled together. The clutch rings H and 12 are operated in unison by a double fork 13 described more in detail hereinafter.

A similar clutch ring 14 is mounted upon the toothed clutch member 59 for axial sliding movement thereon. In Figure 3 the clutch ring 14 is shown in its central or neutral position. Inasmuch as the clutch member 49 is splined to the countershaft 22, it will be seen that when the clutch ring 74 is shifted forwardly to engage the clutch teeth 48 on the gear 43, the gear 46 will be locked to the countershaft 22. On the other hand, when the clutch ring 74 i shifted rearwardly into engagement with the clutch teeth 53 carried by the gear 50, the gear 53 will be locked to the countershaft 22. The clutch ring 74 is shifted by a fork '56, to he described more in detail later.

With reference now to the driven shaft 23, a clutch ring H is slideably mounted upon the periphery of the toothed clutch member 6! and is actuated by a double fork H3. The clutch ring E1 is shown in Figure 3 in its central or neutral position, and it will be seen that when it is shifted forwardly into engagement with the clutch teeth 59 on the gear 53 the latter gear will be coupled to the driven shaft 23.

Attention is now directed to the idler shaft 2A. A clutch ring is is slideably mounted upon the periphery of the toothed clutch member 69 which 3 in turn i splined to the hub 34 of the gear 33. The clutch ring it is adapted to be slideably moved by the double fork 78, and when shifted rearwardly engages clutch teeth 68 on gear 6'. to lock gears 36 and 6? together for rotation as a unit.

Shift pattern Referring briefly to the shift pattern shown in Figure 15 will be noted that the gear ratios are divided between a low range and a high range of speed ratios. The low range includes first, second and fourth speeds forward and a reverse, while the high range includes third, fifth and sixth speed forward and a reverse.

Low rangefirst speed Selection between the low and high ranges of speed ratios is effected by actuation of the double fork 33 which simultaneously shifts clutch rings H and i2. Shifting the clutch rings to the left in Figure 3 or forwardly of the transmission, causes clutch ring 72 to straddle clutch teeth 44 and =3? and to lock gear 53 and 43 together. For all speeds in the low range, therefore, the power flow begins through gear 32 on the driveshaft 2| and gears 43 and it on the countershaft 22. First speed is effected after the transmission has been shifted into low range as previously described, by shifting clutch ring 14 to the right in Figure 3 so that the clutch ring straddle the teeth on the clutch member 43 and the clutch teeth 5| on the gear 53 to lock gear 50 to the countershaft 22.

The power flow in first speed is through the following gears in the order recited: gear 32 carried by driveshaft 2!, gear 43 rotatably mounted on countershaft 22, gear 46 coupled to gear 43 by the clutch ring i2, gear 38 of the cluster gear 34 journaled on the driveshaft 2|, gear 39 integrally formed with gear 38 on the cluster gear,

the driven shaft 23. F tremely low reverse speed is thus obtained.

gear 50 coupled to the countershaft 22 by the clutch ring 14, gear 52 carried by the countershaft 22, and finally gear 62 carried by the driven shaft 23 and thence to the drive pinion 5'! and the rear axle assembly. It will be noted that the incorporation of the cluster gear 34 into the gear train in first speed make it possible to obtain an extremely large reduction. In the present instance a total reduction in first speed of 154 to 1 is obtained, the tractor speed at the normal engine speed of 1500 R. P. M. being 1.5 miles per hour. This affords a creeping speed in first gear which may be used when plowing under heavy conditions, or with transplanters, orchard sprayers, and other implements requiring an extremely low peed.

Low range-second speed power flow for second speed is through gears 32,

43, 46, 52 and 62 to the driven shaft 23. A reduction of 64 to 1 is obtained in second speed with a tractor speed of 3.5 miles per hour at 1500 R. P. M. engine speed. This speed is the one most generally used for normal plowing.

Low rangefourth speed The next highest low range speed is fourth, and this is effected by shifting the double fork 78 to the left in Figure 3 to shift clutch ring T! to interconnect the clutch teeth on clutch mem her 3! with clutch teeth 59 on gear 58 and to therefore couple gear 58 to the driven shaft 23. The power flow from the driveshaft 2| to the driven shaft 23 for fourth speed is through gears 32, 43, 46, and 53 to the driven shaft 23. Fourth speed gives a reduction of 38 to 1 and a tractor speed of six mile per hour and may be used for extremely light plowing or for tillage where a reasonably fast speed can be used without damage to crops, such as with spike tooth narrows and similar implements.

Low range-reverse Low range also includes a reverse speed reduction of 154 to 1 with a reverse tractor speed of 1.5 miles per hour. This is effected by shifting the double fork 78 to the right in Figure 3 to shift clutch ring 19 to couple together the clutch teeth on clutch member 69 and clutch teeth 58 on gear 61, thus locking gears 66 and 6'! together for rotation as a unit. Inasmuch as gear 81 on the idler shaft 24 is in constant mesh with gear 50 on the countershaft 22, it will be seen that this again brings the cluster gear 34 into the power train, the latter comprising the following gears in order: 32, 43, 45, 38, 39, 50, 6'5, 63, and 62 to It will be seen that an ex- High range-thzrd speed The three forward and one reverse speeds available in high range can be readily obtained by first shifting the double fork F3 to the right in Figure 3 to place clutch ring 12 on the countershaft 22 in an inoperative position and at the same time to shift clutch ring II on the drive shaft 2| to a position interconnecting clutch teeth 33 on the drive shaft with clutch teeth 37 on the cluster gear 34. The cluster gear 34 is thus directly driven by the drive shaft 2| and inasmuch as the cluster gear carries two gears 38 and 39, a variety of speeds can be obtained by utilizing one or the other of these gears in the power train.

The lowest speed in high range is third, and is eifected, with the clutch ring ll coupling the cluster gear 3 3 to the drive shaft 2i as described in the preceding paragraph, by shifting clutch ring '14 to the right to connect gear 50 to the countershaft 2?. through the clutch member 49. The power flow in third speed is from the drive shaft 25 to the cluster gear 34, thence through gears 39 5% to the countershaft 22, and then from gear 52 on the countershaft to gear $2 on the driven shaft 23. The reduction in third speed is 49 to 1 with a tractor speed of 4.5, and this gear ratio is suitable for all plowing of a lighter nature where additional speed can be use High range-fifth speed Shifting clutch ring it to the left obtains fifth speed forwar by coupling gear 35 to the countershaft 22 through the clutch member iii, in a manner similar to the shift required in second speed of low range. The power flow is again from the drive shaft fl to the cluster gear 3% but in this instance is from gear 38 of the cluster gear to gear 45, the latter being coupled to the countershaft 22 through the clutch member as, and finally through gears 52 and 82 to the driven shaft 23. The reduction in fifth is 21 to 1 resulting in a tractor speed at 1590 R. P. M. of 11 miles per hour, which is a suitable speed for road transport of the tractor.

High range-sixth speed The fastest forward speed, or sixth, is effected by shifting the double fork E8 to the left in Figure 3, to shift clutch ring T! and couple gear 8 to shaft 23, the power flow now being from drive shaft ft to the cluster gear 3 3 and from gear 38 on the cluster gear to gear 36 which freely rotates about the countershaft 22, and thence to gear 53 now coupled to the driven shaft 23 by the clutch ring 7'1. Sixth speed gives a total reduction of 12 to 1 and a tractor speed of 18.6 miles per hour, which affords a fast transport speed for driving the tractor on the road without implements.

High range-reverse A. reverse speed is also available in high range, and is effected by shifting the double fork T5 to the right, to shift clutch ring "it and couple gears 65 and ET together. T he power fiow is from drive shaft 2i to the cluster gear 3 as in all high range speeds, and thence through gears 39, 58,

i, 65 and to the driven shaft It will be understood that the uses of the various gear ratios briefly discussed above are only given by way of example and that various other uses for the particular ratios exist. The six for ward gear ratios obtainable with the present tranmission are ideally suited for various tractor operations. The two reverse ratios obtainable, one in low range and the other in high range, simplify gearshifting since areverse speed is readily obtainable regardless of the particular forward speed in which the tractor is operating. In the majority of instances the low reverse obtainable in low range will be the one to be used when the tractor is operating in a low range forward speed ratio, and the high reverse obtainable in high range will be the most suitable reverse ratio under the circumstances existing when the tractor has been operating in one of the high range forward speed ratios. While this simplifies the gearshifting, obviously, however, either reverse may be obtained at any time.

It will be noted that the various gear ratios briefly'discussed above are obtained with a very compact transmission arrangement incorporating only ten gears. Furthermore, relatively heavy loads may be carried since the gears are all mounted upon short shafts with a relatively short distance between bearings.

Shift mechanism The construction of the shift mechanism for the transmission will be best understood by referring first to Figures 4, 5 and 14. Adjacent the bottom of the transmission housing 12 is a longitudinally extending shifter rail ii! in the form of a rod. At its forward end the shifter rail 8! is slideably mounted in a bracket 82 integrally formed with the transmission housing. At its rearward end the shifter rail extends through an opening 33 in the intermediate wall 3! of the housing. A series of three arcuate grooves 8:? are formed in the lower surface of the shifter rail 8| near its rearward end to permit the rail to be indexed in three longitudinally spaced positions. The indexing is accomplished by a ball 86 urged into engagement with the notches M by means of a spring 81. The ball and spring 8'! are mounted in a bore 88 in the wall 31 of the housing and are held therein by a stud 89.

As best seen in Figures 4 and 14, the double fork i8 is mounted upon the shifter rail 8 I, being held thereon by a set screw 99 and lock nut 9|. The double fork 18 has bifurcated portions 92 which are reduced in thickness and are adapted to be received within the peripheral grooves formed in the clutch rings 1'! and if). It will be apparent that longitudinal movement of the shifter rail 81 is effective through the shifter forl; (8 to simultaneously shift the clutch rings 1! and '59 between three positions. The central position places both clutches in neutral, the forward position effects an engagement of clutch ring Ti and the rearward position effects an engagement of clutch ring 19.

Referring now to Figure 5, there is mounted upon the lower shifter rail 8 i, and held thereon by a set screw 93, a lug S4. The lug 34 is adapted to be alternately engaged by a shifter arm or an interlock bracket to control the longitudinal position of the shifter rail 8! and the shifter for}; H3, as will be described more in detail later.

A pair of longitudinally extending shifter rails 88 and 9? are mounted adjacent the upper portion of the transmission housing E2, the rails being slideable at their opposite ends in the walls 28 and 3i of the transmission housing !2. The rearward end of the shifter rail 96 is formed with a series of three arcuate notches 98 arranged for indexing engagement with a ball 99 held against the rail by a spring Hit. As seen in Figures 4A, the rearward end of shifter rail 9'! is provided with two longitudinally spaced notches I02 arranged for indexing engagement with a. ball I03 urged against the rail by a spring led.

As shown in Figures 4 and i l, the fork it is rigidly mounted upon the shifter rail by means of a set screw l96 and :1 lock nut 58?. The fork 16 has bifurcated portions I68 reduced in thickness and engageable within the peripheral groove formed in shifter ring 14 which in turn is slideably mounted upon the clutch member 39.

Near its forward end the shifter rail 93 carries a shifter lug I09, Figure 5, rigidly mounted thereon by means of a set screw I l l and a lock nut l 12. The shifter lug IE9 is adapted to be shifted between three longitudinal positions, by means of shifting mechanism to be described later, to shift the clutch ring i l.

Referring now to Figure 5, the shifter rail 91 carries the double shifter fork '53, the latter being secured to the rail by means of a set screw I I 3 and a lock nut H2. The shifter fork I3 has bifurcated portions H3 reduced in thickness to fit in the peripheral grooves formed on the clutch rings II and i2. A laterally projecting lug H1 is integrally formed on the shifter fork I3 and is adapted to be actuated by the shifting mechanism to be described hereinafter to shift the shifter rail 91 and the fork l3 longitudinally between the two index positions shown in Figure 4A. As previously discussed in connection with the transmission gearing, one of these positions places the transmission in low range and the other in high range.

The mechanism for Shl'i. ting the above-described shifter rails includes a vertically mounted shifter shaft I positioned at the left side of the trans mission housing I2 at the lower end thereof, as best shown in Figures 4 and 5. At its lower end the shifter shaft 52f is slideably mounted in a boss I22 integrally formed with the lower portion of the transmission casing. At its upper end the shifter shaft I2! extends through a bushing I23 pressed into an opening in the transmission cover I24.

The extreme upper end of the shifter shaft I2I is keyed to a shift lever I26 extending upwardly rearwardly and inwardly toward the drivers position. The upper end of the gearshift lever I26 carries a knob 82? for operation by the driver.

The lower portion of the gaershift lever I 26 is formed in the shape of an inverted cup and houses the upper end of a coil spring 28 with the upper end of the spring bearing against a shoulder on the gearshift lever and the lower end resting upon a washer 529 seated upon the bushing I23. A sheet metal shield 23f is pressed into the inverted cup shaped portion of the gearshift lever I25 and encloses the upper end of the bushing I23 to protect the assembly from the weather.

It will be apparent from the foregoing that the shifter shaft 52! is mounted in the transmission for rotary movement and also for vertical sliding movement, under the control of the driver through manipulation of the gearshift lever I26. The vertical and rotary position of the shifter shaft IN, and accordingly the gear ratio to which the transmission has been shifted at any time, is indicated on a shift pattern plate I32 shown diagrammatically in Figure 4. As best seen in Figure 15, the plate Q32 is riveted to a bracket I33 which in turn is suitably mounted upon the upper surface of the upper transmission housing in position to be viewed by the vehicle operator. The plate 32 has engraved or suitably displayed thereon a shift pattern I33 indicating the six forward speed positions and the two reverse speed posi tions, as well as the two neutral positions.

Mounted upon the upper end of the shifter shaft IZI, Figure 4, is a pointer I35 suitably secured thereon by a nut E37. The forward end of the pointer is positioned closely adjacent the plate I32 and as the gearshift lever I 25 and the shifter shaft I2l are moved vertically and angularly between the various indexed positions, the particular position is indicated on the shift pattern I34 by the pointer I36, enabling the operator to not only ascertain the particular speed ratio in which the tractor is operating, but also to determine the CPI 10 movement necessary to shift to any other desired speed ratio.

As best seen in Figure 5, a pair of shifter arms MI and I42 are suitably welded or brazed to the shifter shaft IZI. The arm I M is adapted to be engaged with the lugs H39 and II? to shift the upper shifter rails 96 and 37, While the shifter arm I42 is adapted to be engaged with the lug 94 to shift the lower shifter rail 8 I.

Figures 8 and 8A show the upper shifter arm l il in engagement with the lug I39 carried by the shifter rail 95. The lug I69 has a pair of notches H13 and I 54 adapted to receive the enlarged end portion hit of the shifter arm on. Depending upon the angular position of the shifter shaft l2I the arm I ll engages the notch I 43 for low range speeds and the notch Hi l for high range speeds.

Figures 9 and 9A show the upper arm I ii in engagement with a notch It! formed in the lug II! carried by the fork l3. Angular movement of the shifter shaft I 2| moves the fork l3 and shifter rail 9? longitudinally between the positions shown in Figures 9 and 9A.

Figures 10 and 10A show the lower shifter arm I 42 engaging the lug 9 2 on the shifter rail iii. The lug 91; has a pair of notches I 38 and Its, the former belng engaged by the enlarged head iii! of the arm M2 for low range operation and the latter being engaged by the arm for high range operation.

To prevent the forks and lugs from being inadvertently shifted from their neutral positions while one particular fork and lug is being moved by the adjacent shifter arm, upper and lower interlock brackets I52 and IE3 are provided. These two brackets are identical in construction, and differ only in that they are inverted during assembly. Consequently only one will be described in detail.

The lower bracket I53 is best shown in Figures 4, 5 and 12, and comprises a crescent shaped member having parallel bores I53 formed in its bifurcated end portions. The bores I54 in the bifurcated end portions of the interlock brackets slideably receive rods I56 and I57 vertically mounted in the transmission housing. The lower ends of the rods are seated in the boss I22 integrally formed with the transmission casing l2 while the upper ends are received within bores formed in a bracket I58. The bracket 58 has legs I59 secured to the upper flange of the transmission casing I2 by means of bolts IcI. As best seen in Figure 12, the intermediate portion of the interlock bracket I53 is formed with a pair of flanges I62 and IE3 adapted to be engaged within the notches I 48 and lit formed in the lug carried on the shifter rail 8|. With the interlock bracket I53 and the lug 93 thus engaged, longitudinal movement of the shifter rail 8! and the fork I8 carried thereby is prevented.

Referring now to Figure 5 it will be seen that the inwardly projecting intermediate portion of the interlock bracket I53 is formed with a groove I64 through which the shifter arm hi2 extends. The separated portions of the flanges I62 and I 63 thus straddle the shifter arm Hi2. Inasmuch as the shifter arm M2 is secured to the vertical shifter shaft I2I, vertical movement of the shaft results in corresponding vertical movement of the interlock bracket I53, the latter freely sliding on the rods I56 and I51.

As previously mentioned, the upper interlock bracket I52 is identical in construction to the lower bracket I53 but is mounted in inverted position, and straddles the shifter arm MI. The upper end of the shifter shaft I2I is provided with an annular groove I66 arranged to be indexed by a ball If? urged'against the shaft by a spring E68. Engagement between the ball I57 and the groove I35 is effected when the shaft is in its central position at which time the trans mission is in neutral.

In addition to providing interlock mechanism effective to prevent the transmission from being shifted inadvertently, means are provided for preventing the starter from being actuated except when the transmission is in neutral. This means comprises a starter interlock bracket I69 having a hub encircling the shifter shaft I21. The bracket I53 is positioned longitudinally of the shaft between the upper portion of the bracket I58 and a retaining plate III held by means of bolts I2 adjacent'the lower portion of outwardly extending integral flanges I73 of the bracket I53. While the starter interlock bracket I5?! is freely rotatably mounted on the shifter shaft IZI, it is constrained to move angularly with the shaft by means of downwardly extending bifurcations I'M straddling an intermediate portion of the upper shifter arm I6 I.

Also integrally formed with the starter interlock bracket IE9 is a horizontally extending flange I1 8 best seen in Figure 13 as being quad rant shaped. The flange H6 is provided with a pair of angularly spaced holes II"! and "I18 suitably positioned for engagement with a downwardly projecting pin I'r9' of a starter button IEI when the transmission is-in neutral. Inasmuch as the transmission has two indexed neutral positions, one for low range and another for high range, the two holes I1? and I?!) are necessary to permit the starter to be actuated when the transmission is in'neutral, low range, and also when it is in neutral, high range. At all other times the flange I'IIi of the interlock bracket-I69 prevents depression of the starter button I8I by intercepting the movement of the pin I'i'a, thus preventing the starter from being operated-except when the transmission is in'neutraland the drive to the rear wheels disconnected.

Shift mechanismoperation As previously mentioned, the shiftershaft I-ZI is adapted to be reciprocated vertically and also moved angularly-by manipulation-of the gearshift lever I26 bythe driver. he-shaft maybe reciprocated vertically between three positions. Figuresb, 6, and 7 respectively show the upper,

central, and lowermost positions of the vertical shifter shaft 2L Reference is firstmade to Figure 6, showing the central position ofthe-vertical shifter shaft, in-which position the index-ball IE9 is in engagement with the annular groove +65 formed in the upper portion of the shaft. The engagement between the ball and groove is-suificient to hold the shaft in this position, and to overcome the tendency of thespring I28 at the upper end of the shaft to shift the shaft upwardly. Referring to Figures 9-and 9A as well as to Figure 6, when the shifter shaft I-2I is-in its central or neutral position the upper arm MI engages the notch It? in the lugI I-l carried-by the double fork 13. At this time the lever I26 can be manipulated to move the shifter shaft I2 I angularly. Movement in a counterclockwise direction shifts the shifter rail '91 forwardly of the transmission to the position shown in Figure 9, while angular movement in a clockwise direction shifts the fork and rail rearwardly to the position shown in Figure 9A. These two positions are indexed by means of the notches I02 and balls I03 arranged at the rearward end of the rail 97 as shown in Figure 4A. In the position shown in Figure 9 the shifter shaft IZI is located in its neutral position for low range operation while in the position shown in Figure 9A the shaft is positioned in neutral position for high range operation. These positions are suitably indicated upon the shift pattern I34, Figure 15, by the pointer I36, and bear the indices NL for neutral, low range, and NH for neutral, high range.

With the vertical shifter shaft I2I in its central or neutral position, as shown in Figure 6, and with the transmission thus in either neutral, low range, or neutral, high range, it is desirable to prevent inadvertent shifting of the shifter rails B G and 8 I. This is accomplished by the upper and lower interlock brackets I52 and I53 respectively which engage the lugs I09 and 94 mounted upon the shifter rails 96 and 8| respectively. Inasmuch as the non-rotatable interlock brackets I52 and I53 are engaged respectively with the lugs I09 and 94, inadvertent operation of the rails 96 and Ill is prevented.

From the neutral position shown in Figures 9 and 9A, the transmission may be shifted to first and second speeds in low range and to third and fifth speeds in high range by shifting the vertical shifter shaft upwardly to its uppermost position and then rotating it either clockwise or counterclockwise depending upon the particular speed range desired. Reference is made to Figure 5 and to Figures 8 and 8A showing the uppermost position of the shifter shaft. In the uppermost position the upper shifter arm MI engages either the notch I43 or the notch Hi l in the lug I09 on the shifter rail $6 depending upon whether the transmission is being shifted from neutral, low range or neutral, high range.

Figure 8 shows the position for neutral, low range, and it will be seen that subsequent angular movement of the gearshift lever and the shifter shaft I2I from the neutral position effects various speed ranges. With the shifter shaft and the upper shift arm MI in neutral, low range, Figure 8, clockwise movement of the shaft is effective to shift the shifter rail 96 rearwardly to place the transmission in first speed, while movement in a counterclockwise direction from the neutral position is effective to shift the shifter rail forwardly and to shift the transmission into second speed. Inasmuch as the manner in which the particular clutches are actuated by the shifter rails has been described in detail hereinbefore, no attempt will be made to duplicate this description at this time.

As seen in Figure 8A, in neutral, high range, the shifter arm I il engages the notch HM in the lug II9 on the shifter rail 56. Clockwise movement of the shifter shaft i2I is effective to shift the transmission into third speed while counterclockwise movement of the shaft shifts the transmission into fifth speed in the manner more fully described earlier in the specification.

It will be noted from Figure 5 that with the shifter shaft I2! in its uppermost position the interlock brackets I52 and IE3 are in engagement with the lugs III and 9 respectively to hold the shifter rails 91 and 8| against inadvertent movement.

Reference is now made to'Figure '7 which shows the shifter shaft I2I in its lower position. In this position the upper interlock bracket I52 engages the upper lugs I09 and II! to prevent inadvertent shifting of the shifter shafts 9B and. 9? respectively. The lower shift arm M2 engages the lug 34 to permit the lower shifter rail 8! to be shifted longitudinally upon rotary movement of the shifter shaft. Figure 10 shows the position of the shifter shaft [2! and the arm i512 for neutral, low range, with the end arm in engagement with the notch of the lug es on the shifter rail 8!. It will apparent that clockwise movement of the shaft and arm shifts the transmission to reverse, low range, while counterclockwise movement from the neutral position shifts the transmission to fourth speed forward.

Figure 10A shows the shifter shaft 12! and lower M2 in position for neutral, high range, with the end of the arm in engagement with the notch its of the lug. From this position the transmission may be shifted into reverse, high range, by clockwise movement of the shaft and into sixth speed forward by counterclockwise movement of the shaft.

As previously mentioned the various gear ratios are indicated in Figure 15 upon the shift pattern i3? and it will be apparent that the driver can readily select the particular ratio desired and make the necessary shift by reciprocating the gearshift lever Vertically and rotating it until the pointer 536 is directed toward the desired index. It will be seen that the shift mechanism is compactly located at one side of the transmission housing and contains a minimum of parts, and furthermore that the interlock mechanism automatically permits one shifter rail to be shifted while preventing movement of the other two shifter rails so that operation of the transmission will be positive at all times.

W e claim:

1. In a variable speed power transmission having a transmission housing containing a drive shaft, a countershaft, an idler shaft and a driven shaft with inter-meshing gears on said shafts and clutch means arranged to selectively couple certain of said gears to each other and to said shafts to obtain various gear ratios between said drive and driven shafts, the combination of vertically spaced horizontally extending shifter rails mounted in said housing, reciprocable forks on said rails engaging said clutch means to operate the latter, a vertically extending shifter shaft mounted in said housing for vertical reciprocation and also for angular movement, a manually operable lever connected to said vertical shifter shaft to operate the latter, 2. lug carried by each of said shifter rails and extending toward said vertical shifter shaft, each of said lugs having a pair of axially spaced slots formed therein, and shifter arms carried by said vertical shifter shaft, said arms being selectively engageable with the slots in said lugs to shift said rails between different operating positions.

2. The structure defined by claim 1 which is further characterized in that said arms and lugs are arranged so that in one vertical position of said vertical shifter shaft one arm is in engagement with its respective lug while the other arm is vertically spaced from its respective lug and so that in a second vertical position of said shifter shaft the second arm is in engagement with its respective lug while the first arm is vertically spaced from its respective lug, and interlock mechanism movable with said vertical shifter shaft, said interlock mechanism being arranged to selectively hold each. of said lugs against inadvertent reciprocation while the other lug is being operated by its respective shifter arm.

3. The structure defined by claim 1 which is further characterized in that an interlock bracket is associated with each of said shifter arms and is mounted for vertical reciprocation therewith as the shifter shaft is moved between different vertical positions, guide means within said housmg supporting said interlock mechanisms and permitting vertical movement of the latter while preventing angular movement thereof, said interlock mechanisms being selectively engageable with the shifter lugs to prevent inadvertent reciprocation of the latter except when the lugs are engaged bysaid shifter arms.

4. Thestructure defined by claim 1 which is further characterized in that a starter button is mounted upon said housing and has a pin projecting downwardly therefrom, a starter interlock bracket mounted in said housing for angular movement with said vertical shifter shaft, said starter interlock bracket having a flange provided with a pair of 'angularly spaced openings therein, said openings being arranged in such manner as to be in alignment with said pin when the. shaft is in the proper angular position to permit engagement between the shifter arms and either of the slots formed in the lugs carried by the shifter rails, the flange on said starter interlock bracket blocking movement of said pin and preventing operation of the starter button in all other angular positions of the shifter shaft so that said starter button can be operated only when the transmission is in either of its two neutral positions.

5. In a variable speed power transmission having a transmission housing containing a drive shaft, a countershaft, an idler shaft and a driven shaft and inter-meshing gears on said shafts and clutch means arranged to selectively couple certain of said gears to each other and to said shafts to obtain various gear ratios between said drive and driven shafts, the combination of three horizontally extending shifter rails reciprocably mounted in said housing, forks carried by said shifter rails engageable with said clutch means respectively to operate the latter, three vertically spaced lugs carried respectively by said shifter rails, a vertically extending shifter shaft mounted in said housing for vertical reciprocation as well as for angular movement, shifter arms carried by said shifter shaft and engageable with slots formed in said lugs, a manually operable lever for shifting said vertical shifter shaft between three vertically spaced positions, one of said shifter arms being engageable with one of said lugs in the central position of said shifter shaft and effective upon angular movement or" said shifter shaft to reciprocate said last-mentioned lug between two positions each operable to place said transmission gearing in neutral, another of said shifter arms upon movement of said shifter shaft to its uppermost position being engageable with another of said lugs in one of two slots formed therein depending upon the angular position of said shifter shaft and effective upon further angular movement of said shifter shaft to reciprocate said last-mentioned lug and effect a plurality of various gear ratios, and the other of said shifter arms upon movement of said shifter shaft to its lowermost position being engageable with another of said lugs in one of two slots formed therein depending upon the angular position of said shifter shaft and effective upon further angular movement of said shifter shaft to effect various other gear ratios.

6. The structure defined by claim 5 which is further characterized in that interlocking means with first-c1utch means onsaid-- drivershat andiio:

second and third; clutch meansziomsaid" eoimterav shaft, said intermeshing gears meludingsaxeluster; gear on said drivewshaftnand, ifirst; seeondiiandz third, gears onsaid countershaft;;the, combinati0n of a pair of: shifter rails.nnountedninasaid ihoussL 152-:

ns; a le Ql' imollnteth111301130118 of said railsi for reciprocation and;-engageab1e "with said firsti t i d-mentioned :clutch means :to simultana:v ousiy shift :the latter, a second iforksmountedsupa a.

on the? other of 1 said-shifter; rails Jon: reciprooa-s 20:

tion and ,engageabiehwithzthe seeond-mentioned clutch meansitozshiitthe latter, aimanualiwopm erable shifter shaft mountedimsaidihousingzfon: reciprocation and raise-ion an'gulanmovemenhi. ashiiter arm. carriedtioy-- saidshatt-zand, operativeiy 25 engageablewith meanscarried:bysaid shiftenrailin one. axial position of. saidishiiter shaft; angular movement of saidshifteri shaft between two-angular POSitiQns when theishiftershaft isinptl'ie;- 1ast;=ment ioned; 1 axial vposition being; effective to shift:said.;donb1e -fork and said first and thirdmentioned clutch means between one positionin 1 whichsaid firstmentioned clutch means connects, said cluster gear tov said drivershaft and a second position in which said third-mentioned clutch; means connects the first and second gears oi; said countershaft together, and said shifter arm: being engageable with means carried by the otherdof-said shifterrailsowhen said shifter shaft hasbeen axially moved from its first-mentioned position, further angular movement of said shifter shaft when in the latter position being efiective tO'ODEIatQ; said secondementioned clutch means to; selectively connectv either said, second; or said;

thirdsgear, 011;,said countershaft to said counter,-

shaft- HAROLD 'L; BROOK: JAMES. R. STEVENSON:

References Cited in the file-of this patent UNITEDVSTATES PATENTS Number- Name Date 2,515,710;v Holmes; July 18, 1950,: 2;5 21;312' Siekmann septa 5, 1950 2,569,341 Schjolin Sept. 25; 1951 

